Image Sensor Device and Method of Forming Same
An image sensor device includes a pixel array, a control circuit, an interconnect structure, and a conductive layer. The pixel array is disposed on a device substrate within a pixel region. The control circuit disposed on the device substrate within a circuit region, the control circuit being adjacent and electrically coupled to the pixel array. The interconnect structure overlies and electrically connects the control circuit and the pixel array. The interconnect structure includes interconnect metal layers separated from each other by inter-metal dielectric layers and vias that electrically connect between metal traces of the interconnect layers. The conductive layer disposed over the interconnect structure and electrically connected to the interconnect structure by an upper via disposed through an upper inter-metal dielectric layer therebetween. The conductive layer extends laterally within outermost edges of the interconnect structure and within the pixel region and the circuit region.
This Application is a Continuation of U.S. application Ser. No. 15/714,043, filed on Sep. 25, 2017, which is a Continuation of U.S. application Ser. No. 14/856,624, filed on Sep. 17, 2015 (now U.S. Pat. No. 9,773,828, issued on Sep. 26, 2017), which is a Continuation of U.S. application Ser. No. 12/708,167, filed on Feb. 18, 2010 (now U.S. Pat. No. 9,142,586, issued on Sep. 22, 2015), which claims the benefit of U.S. Provisional Application No. 61/154,940, filed on Feb. 24, 2009. The contents of the above-referenced Patent Applications are hereby incorporated by reference in their entirety.
RELATED APPLICATIONSThe present application is related to U.S. Non-Provisional Patent Application entitled “Front Side Implanted Guard Ring Structure for Backside” bearing attorney docket No. T5057-K014U (TSMC2008-0924) (U.S. application Ser. No. 12/710,862) which is based on, and claims priority from, U.S. Provisional Application No. 61/154,955, filed on Feb. 25, 2009. The disclosures of the above-listed applications are hereby incorporated by reference herein in their entirety.
The present application is further related to U.S. Non-Provisional Patent Applications: “Pad Structure for 3D Integrated Circuit” by Tsai et al., having Patent Application Publication No. U.S. 2009/0278251, “Through Via Process” by Chiou et al., having Patent Application Publication No. U.S. 2009/0224405 and “Through-Substrate Via for Semiconductor Device” by Kuo et al., having Patent Application Publication No. U.S. 2009/0051039, all of which are expressly incorporated by reference herein in their entirety.
BACKGROUNDThe present disclosure relates generally to semiconductor devices, and more particularly, to a pad structure for backside illuminated image sensors and methods of forming same.
Image sensors provide a grid of pixels, such as photosensitive diodes or photodiodes, reset transistors, source follower transistors, pinned layer photodiodes, and/or transfer transistors, for recording an intensity or brightness of light. The pixel responds to the light by accumulating charge carriers (such as electrons and/or holes) generated when the light passes into/through a silicon layer. The more light, the more charge carriers are generated. The charge carriers are picked-up by sensors and converted into an electric signal subsequently usable by other circuits to provide color and brightness information for suitable applications, such as digital cameras. Common types of pixel grids include a charge-coupled device (CCD) or complementary metal oxide semiconductor (CMOS) image sensor (CIS) formed on a silicon semiconductor die. A semiconductor chip, when incorporated in an electronic circuit, communicates with the outside world through various input/output (I/O) pads, such as signal pads, and power/ground (P/G) pads.
The image sensor device 100 of
However, although useful in obviating the problems associated with dishing, the notched slotted metal layer 120 wastes valuable wafer space, i.e., reduces otherwise usable wafer space.
Several particular embodiments will be illustrated by way of example, and not by limitation, in the figures of the accompanying drawings in which elements having the same reference numeral designations represent like elements throughout and wherein:
The present disclosure provides, in accordance with one or more embodiments, wafer level processing (WLP) techniques for a backside illuminated pixel sensor device that maximizes available wafer area and/or improves electrical I/O characteristics of the sensor device by using solid conductors in a conducting layer, also known as a top conducting layer, or a top metal layer, (hereinafter referred to as “TME” layer), and a through silicon via (TSV) to maximize available wafer area and improve electrical I/O characteristics of the sensor device.
Various examples of TSVs incorporated in IC chips are disclosed, for example, in U.S. Patent Application Publications Nos. 2009/0224405, US 2009/0051039, and 2009/0278251, the collective subject matter of which is hereby incorporated by reference herein in their entirety.
In at least one embodiment, a multi-layer interconnect (MLI) layer 218 is formed on the first side 250a of the device substrate 250 overlying pixel array 204 and control circuit 206, and, in at least one embodiment, MLI 218 includes at least two, for example as depicted three, interconnect layers M1-M3 separated from each other and from a TME layer 219 by IMD (inter-metal dielectric) layers 234a-d. Each interconnect layer M1-M3 comprises metal traces that electrically connect portions in each metal layer M1-M3. The metal traces in each interconnect layer M1-M3 are separated by a dielectric 217 that comprises similar materials to the materials used to form IMD layers 234a-d. IMD layers 234a-d also include vias 216 that electrically connect between the metal traces different interconnect layers M1-M3. In at least one embodiment, IMD layers 234a-d comprise materials such as silicon dioxide, silicon nitride, silicon oxynitride, polyimide, spin-on glass (SOG), fluoride-doped silicate glass (FSG), carbon doped silicon oxide, BLACK DIAMOND™ (available from Applied Materials of Santa Clara, Calif.), XEROGEL™, AEROGEL™, amorphous fluorinated carbon, Parylene, BCB (bis-benzocyclobutenes), SILK™ (available from Dow Chemical of Midland, Mich.), polyimide, and/or other suitable materials. In at least one embodiment, the IMD layers are formed by a technique including spin-on, CVD, sputtering, or other suitable processes.
In some embodiments, interconnect layers M1-M3 and the vias 216 include a metal or metal alloy (e.g., Al, Cu, or Ag), a metal silicide, etc., and provide electrical connectivity between pixel array 204 and control circuit 206, as well as between control circuit 206 and TME 219. Based upon the internal and external interconnection requirements of pixel array 204 and control circuit 206, interconnect layers M1-M3 are electrically interconnected by vias 216 formed by forming via holes that pass through IMD layers 234a-c and disposing a penetrating electrode in each via hole.
TME layer 219 is formed by depositing an electrical conductor, such as a metal or metal alloy (e.g., Al, Cu, or Ag), a metal silicide, etc., overlying IMD layer 234d. After being formed, any excess conductor of TME 219 is removed by planarizing TME layer 219 using, for example, a chemical-mechanical polishing (CMP) process. Unlike the slotted metal pad portions 120 of image sensor device 100, as depicted in
In some embodiments, TME layer 219 routes electrical signals, i.e., I/O signals, power and ground, from control circuit 206 to a respective terminal 228 by means of respective TSVs 222 formed in the carrier substrate 202 within the first region 205. For sake of simplicity, only one terminal 228 and the associated TSV 222 are illustrated in
The carrier substrate 202 is wafer-bonded to the TME layer 219 after the formation of the TME layer 219 is completed. In some embodiments, before the carrier substrate 202 is bonded to TME layer 219, an insulating layer is formed from silicon oxide or silicon nitride on the surface of TME layer 219. This insulating layer prevents electrical connection between TME layer 219 and carrier substrate 202. In other embodiments, this insulating layer is formed on carrier substrate 202 before bonding or insulating layers are formed on both TME layer 219 and carrier substrate 202 before bonding the carrier substrate 202 to TME layer 219.
TSV 222 is formed in the first region 205 after wafer bonding and includes an electrode 224 passing through a via hole 236, which passes through carrier substrate 202. Image sensor device 200 includes a conductive re-routing layer 226 formed on the lower surface 202b of carrier substrate 202 for providing electrical connectivity to terminal 228. In some embodiments, conductive re-routing layer 226 is optional.
As illustrated in
In some embodiments, via hole 236 is formed using laser drilling. However, in at least one alternate embodiment, via hole 236 is formed using a dry etching process, wherein an etching mask is first formed on the bottom surface 202b of carrier substrate 202 to define an opening of via hole 236. Dry etching is then performed using the etching mask to protect semiconductor carrier substrate 202 around the opening. Further, in another alternate embodiment, via hole 236 is formed using a wet etching process.
A spacer insulation layer 238 is formed over the lower surface 202b of carrier substrate 202, including side walls and a bottom of via hole 236 after via hole 236 has been formed. In some embodiments, insulation layer 238 may be formed from silicon oxide or silicon nitride. In some embodiments, insulation layer 238 is formed using chemical vapor deposition (CVD) or spin coating.
The insulation layer 238 is then etched at the bottom of the via hole 236, at 231, to expose the pad portions 220 in TME layer 219. For this purpose, any known or future-developed patterning and etching technique may be used.
In an alternative embodiment, via hole 236 is formed along with the insulation layer 238 before the carrier substrate 202 is bonded to TME 219. In this embodiment, the via hole 236 is formed partially through the carrier substrate 202, followed by the formation of insulation layer 238. The carrier substrate 202 is then thinned from the surface 202a to open the via hole 236 and remove any insulation layer 238 at the bottom of the via hole 236. Subsequently, the substrate 202 is bonded to TME 219.
In one embodiment, electrode 224 is formed using an Aluminum (Al) physical vapor deposition (PVD) deposition method. In other embodiments, electrode 224 is formed by first plating the exposed inner surfaces of the insulation layer 238 in via hole 236 with a seed layer of Cu, and thereafter filling (or partially filing) via hole 236 with one or more conductive materials. The conductive material used to form electrode 224 may comprise a metal (or metal alloy) such as aluminum (Al) or copper (Cu) and/or a metal silicide, etc.
In some embodiments, electrode 224 completely fills the via hole 236 and connects with TME 220. In other embodiments, the electrode 224 covers the surface of insulation layer 238 and connects with TME 219. Further, in some embodiments, electrode 224 includes one or more barrier layers associated with a particular conductive material. The barrier layer(s) and/or conductive layer(s) may be additionally patterned to form re-routing layer 226 on insulation layer 238 formed on the lower surface 202b of semiconductor carrier substrate 202. The re-routing layer 226 may serve as a lateral re-distribution portion of electrode 224, allowing conductive terminal 228 to be placed some distance from via hole 236.
In some embodiments, a separate insulation layer 240 is formed on lower surface 202b of carrier substrate 202 over spacer insulation layer 238 (where present) and exposed portions (e.g., re-routing layer 226) of electrode 224. In some embodiments, insulation layer 240 is formed using chemical vapor deposition (CVD) or spin coating. One or more openings will typically be formed in insulation layer 240 to allow electrical connection of electrode 224 with terminal 228. In the embodiment of
In at least one embodiment, an opening (not shown) in insulation layer 240 that allows connection of re-routing layer 226 to terminal 228 is laterally disposed along re-routing layer 226 of electrode 224. However, in other embodiments, the opening is disposed such that terminal 228 is disposed directly under (i.e., in vertical alignment with) electrode 224. In such embodiments, re-routing layer 226 may be omitted.
In some embodiments, a covering layer 208 is formed above semiconductor device substrate 250, and is formed from a transparent material such as glass in order to facilitate the transmission of incident light to pixel array 204. In some embodiments, a gap 251 is formed between covering layer 208 semiconductor and device substrate 250. In other embodiments, a guard ring structure (not shown), is embedded in semiconductor device substrate 250 directly over pixel array 204 to reduce crosstalk, i.e., scattering of light or charge carriers among neighboring pixels of pixel array 204.
Whether embodied in a system or a semiconductor package, the disclosed image sensor device 200 in one or more embodiments provides improved I/O terminal characteristics and/or helps minimize wafer area that may be wasted due to known CSP processes.
One aspect of the disclosure describes an image sensor device. The image sensor device includes a pixel array, a control circuit, an interconnect structure, and a conductive layer. The pixel array is disposed on a device substrate within a pixel region. The control circuit disposed on the device substrate within a circuit region, the control circuit being adjacent and electrically coupled to the pixel array. The interconnect structure overlies and electrically connects the control circuit and the pixel array. The interconnect structure includes interconnect metal layers separated from each other by inter-metal dielectric layers and vias that electrically connect between metal traces of the interconnect layers. The conductive layer disposed over the interconnect structure and electrically connected to the interconnect structure by an upper via disposed through an upper inter-metal dielectric layer therebetween. The conductive layer extends laterally within outermost edges of the interconnect structure and within the pixel region and the circuit region.
A further aspect of the disclosure describes an image sensor device including a pixel array, a control circuit, an interconnect structure, a conductive layer, a carrier substrate, and a conductive via. The pixel array is disposed on a device substrate within a pixel region. The control circuit is disposed on the device substrate within a circuit region, the control circuit being adjacent and electrically coupled to the pixel array. The interconnect structure overlies and electrically connects the control circuit and the pixel array. The interconnect structure includes interconnect metal layers separated from each other by inter-metal dielectric layers and vias that electrically connect between metal traces of the interconnect layers. The conductive layer is disposed over the interconnect structure and electrically connected to the interconnect structure by an upper via disposed through an upper inter-metal dielectric layer therebetween. The carrier substrate is disposed over the conductive layer. The conductive via is disposed within in the pixel region, passing through the carrier substrate, and partially embedded in the conductive layer.
Another aspect of the disclosure describes an image sensor device including a pixel array, a control circuit, an interconnect structure, a conductive layer, a carrier substrate, and a conductive via. A pixel array is disposed within the pixel region, and a control circuit is disposed within the circuit region electrically coupled to the pixel array. The interconnect structure extends across the pixel region and the circuit region, the interconnect structure including plurality of metal layers stacked over one another and extending. The conductive layer is arranged over the interconnect structure within the pixel region and the circuit region. The conductive layer comprises a solid pad portion disposed within the pixel region directly under the pixel array.
Claims
1. An image sensor device, comprising:
- a pixel array disposed on a device substrate within a pixel region;
- a control circuit disposed on the device substrate within a circuit region, the control circuit being adjacent and electrically coupled to the pixel array,
- an interconnect structure overlying and electrically connecting the control circuit and the pixel array, the interconnect structure including interconnect metal layers separated from each other by inter-metal dielectric layers and vias that electrically connect between metal traces of the interconnect layers; and
- a conductive layer disposed over the interconnect structure and electrically connected to the interconnect structure by an upper via disposed through an upper inter-metal dielectric layer therebetween;
- wherein the conductive layer extends laterally within outermost edges of the interconnect structure and within the pixel region and the circuit region.
2. The image sensor device of claim 1, further comprising:
- a carrier substrate disposed over the conductive layer; and
- a conductive via passing through the carrier substrate and reaching on the conductive layer.
3. The image sensor device of claim 2, wherein the conductive via is disposed within the pixel region.
4. The image sensor device of claim 2, wherein the conductive via is partially embedded in the conductive layer.
5. The image sensor device of claim 2, further comprising a re-routing layer electrically connected to the conductive via at a location in the pixel region.
6. The image sensor device of claim 5, further comprising a terminal on a surface of the re-routing layer, wherein the terminal is electrically connected to the conductive via, and within the pixel region or the circuit region.
7. The image sensor device of claim 1, wherein the conductive layer comprises a device pad portion disposed within the pixel region directly under pixel array.
8. The image sensor device of claim 1, wherein the circuit region extends from the pixel region to an edge of the image sensor device.
9. The image sensor device of claim 1, wherein the upper metal via is disposed within the circuit region.
10. The image sensor device of claim 1, wherein the conductive layer is a solid layer of conductive metal material which extends across the pixel region and the circuit region without any slots therein.
11. An image sensor device, comprising:
- a pixel array disposed on a device substrate within a pixel region;
- a control circuit disposed on the device substrate within a circuit region, the control circuit being adjacent and electrically coupled to the pixel array,
- an interconnect structure overlying and electrically connecting the control circuit and the pixel array, the interconnect structure including interconnect metal layers separated from each other by inter-metal dielectric layers and vias that electrically connect between metal traces of the interconnect layers;
- a conductive layer disposed over the interconnect structure and electrically connected to the interconnect structure by an upper via disposed through an upper inter-metal dielectric layer therebetween;
- a carrier substrate disposed over the conductive layer; and
- a conductive via disposed within in the pixel region, passing through the carrier substrate, and partially embedded in the conductive layer.
12. The image sensor device of claim 11, further comprising an insulation layer surrounding a sidewall of the conductive via and extending on a top surface of the carrier substrate.
13. The image sensor device of claim 12, further comprising a re-routing layer disposed on the conductive via and the insulation layer.
14. The image sensor device of claim 13, wherein the re-routing layer extends across the pixel region and the circuit region.
15. The image sensor device of claim 13, further comprising a terminal on a surface of the re-routing layer, wherein the terminal is electrically connected to the conductive via, and within the pixel region or the circuit region.
16. The image sensor device of claim 11, further comprising a filter element on a backside of the device substrate.
17. The image sensor device of claim 11, wherein the conductive layer comprises a solid pad portion disposed within the pixel region directly under the pixel array.
18. An image sensor device, comprising:
- a pixel region and a circuit region laterally adjacent to the pixel region, wherein a pixel array is disposed within the pixel region, and a control circuit is disposed within the circuit region electrically coupled to the pixel array;
- an interconnect structure extending across the pixel region and the circuit region, the interconnect structure including plurality of metal layers stacked over one another and extending; and
- a conductive layer arranged over the interconnect structure within the pixel region and the circuit region;
- wherein the conductive layer comprises a solid pad portion disposed within the pixel region directly under the pixel array.
19. The image sensor device of claim 18, further comprising:
- a conductive via disposed through a carrier substrate within the pixel region and partially embedded in the conductive layer; and
- a conductive re-routing layer disposed on a backside of the carrier substrate within the pixel region and the circuit region and electrically connected to the conductive via.
20. The image sensor device of claim 18, wherein the pixel region comprises a filter element directly overlying the pixel array on an opposite side of the interconnect structure.
Type: Application
Filed: Apr 18, 2019
Publication Date: Aug 8, 2019
Patent Grant number: 10879297
Inventors: Wen-De Wang (Minsyong Township), Dun-Nian Yaung (Taipei City), Jen-Cheng Liu (Hsinchu City), Chun-Chieh Chuang (Tainan City), Jeng-Shyan Lin (Tainan City)
Application Number: 16/388,071